[1] Malar Hosp, Dept Pediat, Eskilstuna, Sweden
[2] Karolinska Inst, Dept Clin Neurosci, Stockholm, Sweden
[3] Lowenstromska Hosp, Capio Spine Ctr Stockholm, Upplands Vasby, Sweden
[4] Orebro Univ, Dept Med Sci, Orebro, Sweden
[5] Uppsala Univ, Dept Surg Sci, Uppsala, Sweden